There are known technologies that detect collision loads at vehicular collision. In Patent Document 1, collision loads are detected by measuring tension variations of a wire that is horizontally disposed with a given initial tension along the front of a bumper reinforcement.
In Patent Document 2, a pair of parallel conductive wires is horizontally disposed at the front of a vehicle. Collision is detected by determining whether the two wires make contact to each other due to collision impact.
In Patent Document 3, a light-leaking fiber is horizontally disposed along a front bumper of a vehicle. The fiber has a light projecting end unit and a light receiving end unit. Collision is detected by decrease of the receiving light amount in the light receiving end unit; this decrease occurs because of deformation or breakage of the fiber.
There are recently increasing requests about pedestrian protections against vehicular collisions. These requests facilitate proposals of pedestrian protection systems. Here, activating a pedestrian protection system when a collision object is not a pedestrian may cause adverse influence. Therefore, determining whether a collision object is a pedestrian is required.
In Patent Document 4, it is proposed that a pedestrian is determined based on a time period during which a collision load exceeds a given level. Furthermore, in Patent Document 5, a pedestrian is determined based on an increase rate of a collision load after exceeding a given level. Yet furthermore, it is proposed that a pedestrian is determined based on a peak value of a collision load.
In the above technologies, a pedestrian is determined using collision waveforms detected by collision load sensors. Namely, a collision with a pedestrian is determined whether detected collision waveforms fall within a range of waveforms representing a collision with a pedestrian.
Here, when multiple objects collide with a vehicle at the same time, a collision load sensor detects a total of multiple collision loads, thereby decreasing a pedestrian determining accuracy. In detail, there is a case where multiple lightweight objects collide with a vehicle at the same time and then a collision load sensor detects a total of collision loads, thereby mis-determining that the vehicle collides with a pedestrian. In contrast, there is a case where multiple pedestrians collide with a vehicle at the same time and then a collision load sensor detects a total of collision loads from the multiple pedestrians, thereby mis-determining that the vehicle does not collide with a pedestrian.                Patent Document 1: JP-2004-212281 A        Patent Document 2: JP-2004-156945 A        Patent Document 3: JP-H7-190732 A        Patent Document 4: JP-H11-028994 A        Patent Document 5: JP-H11-310095 A        